1. Field of the Invention
The present invention relates to an endless tension belt and a method for fabricating the same, and a resilient endless belt traveling apparatus, which is used for crawler traveling apparatus, transmission belt, or the like.
2. Description of the Related Art
In the resilient endless traveling belt (crawler), the transmission belt or the like to be used in a crawler traveling apparatus for high-speed snow vehicle such as recreational vehicles, construction and civil engineering vehicles, or farm working vehicles, a tension cord is embedded to support the tensile strength acting along the length thereof.
In order to obtain the circumferentially uniform strength characteristics of the tensile strength to avoid difference in rigidity, a technology in which the continuity of reinforcement strength is established by winding and juxtaposing the cord in a spiral fashion is proposed in Japanese Unexamined Patent Publication No. HEI 12-38173.
The related art disclosed in the above-described publication is xe2x80x9cA method of fabricating spiral cords to be embedded in a crawler or the like comprising steps of setting a cord by winding the cord in a spiral fashion around an inner treated rubber layer in the shape of an endless ring, winding an outer treated rubber layer around the inner treated rubber layer and the cord, and clamping the cord layers comprising inner treated rubber layer, a cord, and outer treated rubber layer, and a fabricating apparatus thereforxe2x80x9d, or xe2x80x9cA method of fabricating spiral cords to be embedded in the crawler or the like comprising steps of providing cord groove on the outer peripheral surface of an inner treated rubber layer in the shape of an endless ring at prescribed pitches, setting the cord in the cord groove in a spiral fashion, winding an outer treated rubber layer around the outer periphery of the inner treated rubber layer and the cord, and clamping the cord layers comprising the inner treated rubber layer, a cord, and outer treated rubber layer.xe2x80x9d
However, though the related art is useful in its own way, it has the following problem.
When the three layers of inner treated rubber layer, spiral cord, and outer treated rubber layer are clamped, irregularity of pitches or the like of the cord may often occur, and air encroaches between the layers and, as a consequent, air bubbles formed by the encroached air are trapped between layers, which causes separation of layers.
In addition, it requires an additional and profitless process of forming the cord groove on the inner treated rubber layer, and the cord may come off the groove when the cord is wound along the cord groove, or irregularity of cord may often be occurred due to flowage of rubber since it is three-layer clamped structure.
Accordingly, it is the first object of the present invention to provide an endless tension belt in which a tension cord is orderly arranged without irregularity, and of good quality.
It is the second object of the present invention to provide a method for fabricating high quality endless tension belt in a simple manner.
It is the third object of the present invention to provide a resilient endless belt traveling apparatus that includes the endless tension belt embedded along the length of the resilient endless belt (crawler) to reliably prevent the resilient belt from being stretched, and is suitable for high-speed performance.
The present invention provides an endless tension belt comprising an elongated tension member spirally and juxtaposingly wound into a band-shape, the tension member comprising a tension cord as a core and a rubber-like resilient material for coating the cord along the length thereof, in which the following technical steps are taken in order to achieve the first object described above.
The spiral endless tension belt according to the present invention is characterized in that the tension member formed of rubber-like resilient material has two opposed surfaces, which are formed into flat clamp faces so that the adjacent clamp faces are clamped with each other when the tension member is juxtaposingly wound in a spiral fashion to make it into a band-shape.
In this arrangement, when the elongated tension member is supplied to a winding drum to be wound in a spiral fashion, a tension member supplying position is traversed relative to the drum in the direction of the axis of the drum. Therefore, the adjacent flat clamp faces opposed with each other are applied with a pressure in the direction of the axis of the drum, and as a consequent, these clamp faces are pressedly joined with each other, whereby no air is trapped and thus a homogeneous and high quality endless tension belt is obtained.
The rubber-like resilient material for coating the tension cord, which serves as a core, is preferably in the unvulcanized or semi-cured state.
By juxtaposingly winding the tension member formed of rubber-like resilient material in unvulcanized or semi-cured state in a spiral fashion, joining properties at the joint between the clamp faces of the adjacent tension members is improved.
In addition, preferably, the elongated tension member is formed by coating a single tension cord or a plurality of tension cords juxtaposed at intervals with the rubber-like resilient material, and the tension cord is decentered in the thicknesswise direction of the tension belt by varying the thickness of coating.
In this way, since the tension cord is decentered with respect to the thickness of the tension belt so as to obtain a thicker layer and a thinner layer of the rubber-like resilient material on each side of the cord in the thicknesswise direction of the tension belt, when the belt is embedded into a crawler, the surface of the endless tension belt to be faced with a layer on the outside or inside of the crawler can be selected in accordance with the kind and nature of the outer rubber layer (tread rubber) and the inner rubber layer (rubber in contact with rolling wheel) of the crawler.
In the present invention, preferably, the elongated tension member is juxtaposingly wound around a resilient sheet, juxtaposingly wound around and encapsulated by a canvas bag, or juxtaposingly wound around a resilient sheet and encapsulated by the sheet and the canvas.
The spiral endless tension belt here, as it will be apparent from the description below, is manufactured by winding the elongated tension member in such a manner that the adjacent clamp faces are joined with each other without being piled or separated.
As the tension cord that serves as a core, twisted several steel filaments, a steel cord formed by twisting several bundle of twisted several steel filaments, a cord constructed of filaments of nylon, tetron, or the like as well as the aramid fiber, such as KEVLAR(trademark) (para-phenyleneterephthalamide), and so on may be employed.
The present invention provides a method of fabricating an endless tension belt in which an elongated tension member formed by coating a tension cord that serves as a core with a rubber-like resilient material is wound in a spiral fashion, and the following technological steps are taken in order to achieve the second object described above.
The method is characterized in that when the elongated tension member is supplied to the winding drum, it can be juxtaposingly wound in a spiral fashion around the drum while the flat clamp faces of the rubber-like resilient material of the adjacent tension members are pressedly joined with respect to each other.
Since the endless tension belt is fabricated only by pressedly joining the adjacent clamp faces of the tension member formed of the rubber-like resilient material with respect to each other around the drum, the process of forming the cord groove as required in the related art is not necessary, and irregularity of tension cord that serves as a core is eliminated, and thus a homogeneous and high-quality endless tension belt is provided.
In the method described above, it is preferred that the elongated tension member is wound around the drum in such ways as being juxtaposingly wound around a resilient sheet mounted around the drum, being juxtaposingly wound around and encapsulated by a canvas bag, or being juxtaposingly wound around a resilient sheet and encapsulated by the sheet and a canvas.
In this case, the belt can be manufactured in such a simple manner as supplying the resilient sheet or the canvas to the winding drum and simultaneously supplying the tension member thereon, and then pressedly joining the clamp faces of the tension member with each other. The canvas may be folded into a bag-shape after the belt is formed.
A resilient endless belt traveling apparatus according to the present invention comprises a resilient crawler to be wrapped around a driving wheel and a following wheel in an endless manner, and the following steps are taken in order to achieve the third object described above.
The apparatus is characterized in that the spiral endless tension belt is embedded in the resilient crawler along the length thereof.
Since this arrangement prevents stretch of the crawler along the length thereof by the endless tension belt, uniform rigidity in the entire length of the belt can be obtained, thereby reliably preventing breakage or separation of the cord even when the crawler is subjected to the compression and tension repeatedly during travel.
The rubber-like resilient body of the elongated tension member described above is preferably contains 45-80 weight parts of carbon black (DBP oil absorption 60-120 cm3/100 g, N2SA 65-110 m2/g) per 100 weight parts of polymer component chosen from the group consisting of natural rubber, homo-polymer of conjugated diolefin, co-polymer of conjugated diolefin and ethylene unsaturated monomer, and the composite thereof, and the content of cobalt is 0.03-0.3 wt % of the entire rubber component.
By containing 45-80 weight parts of carbon black, a prescribed hardness, strength and elastic modulus can be obtained for the rubber composition for coating the cord. In other words, when the content of carbon black is less than 45 weight parts, the strength is not sufficient, and in contrast, when the content of carbon black exceeds 80 weight parts, resistance to heat build-up is lowered and thus the deterioration of adherence with respect to the cord is disadvantageously promoted.
In addition, by containing 0.03-0.3 wt % of cobalt, favorable bonding can be formed between the composition and the cord. In other words, when it is below 0.03 wt %, sufficient bonding cannot be obtained, while when 0.3 wt % or more cobalt is contained, deterioration of bonding layer after it is formed is disadvantageously promoted.